Mecca is a city, and it's allowed to enter the city not an issue to Anyone those who are in Saudi Arabia. But there is a diametre maybe of 10 Kms circle from the Kaaba / Haram area. In those 10 Kms circle (5-10 Kms, not sure about the exact distance) Non-Muslims are not allowed as Haram area starts. But while in the Mecca city everyone is allowed.
